Acquisition And Processing Analysis Of Underwater Acoustic Communication Signal

With the continuous development of human society,the use of resources has gradually shifted from land to a larger area of the ocean.The development of underwater communication systems has increased our exploration of marine resources.With the gradual deepening of human exploration activities in the ocean,reliable underwater acoustic communication network has become a hot topic of marine research.But for different sea areas,the test sea conditions are also different.The main purpose of this paper is to test the underwater acoustic communication in Jiaozhou Bay of Qingdao.In this process,we found that the error code,frame loss,failure of normal communication and so on.In order to find out the specific influencing factors,the acoustic signals transmitted in the experiment are collected,processed and analyzed.In this paper,the underwater acoustic communication experiment is taken as the research background.Firstly,the underwater acoustic communication system is summarized in detail,and the channel characteristics of the underwater acoustic communication system are summarized,including propagation loss,shadow fading,Doppler effect,multipath propagation and environmental noise.In view of the complex underwater communication environment,this paper introduces MFSK which is not sensitive to phase and amplitude distortion in the application of modulation technology,and studies its modulation and demodulation mode in detail.Secondly,by testing the ambiguity function derived from autocorrelation of Doppler frequency shift and time delay difference,the advantages of LFM signal in synchronization are further illustrated.It has obvious correlation peak and can achieve synchronous acquisition at the receiver.Therefore,LFM signal is used as synchronous signal to achieve frame synchronization,so as to ensure the underwater acoustic communication network system performance.Then,this paper also studies the underwater acoustic signal processing technology applied in the case of one eighth power transmission when the frame is lost,which is carried out in three aspects:preprocessing,beamforming and post-processing.The main work of this paper is to put forward the underwater communication channel model of Jiaozhou Bay through the experiment in Jiaozhou Bay.Then,in the analysis of FFT transform and low-passfilter in post-processing to remove high-frequency noise,the received data of different transmission power in the transmission distance of 1km is compared horizontally,and the case of frame loss caused by one eighth power transmission is analyzed,and the conclusion that high-frequency noise has great influence is drawn.For the high frequency and low frequency noise,speech enhancement technology and active elimination technology are used in this paper,and it is verified that it can reduce the interference of noise in the underwater acoustic channel to the receiver signal.